|Alan’s September pruning of
trees, shrubs and climbers
As summer turns to autumn, thoughts turn to tidying
the garden after the exuberance of summer and it is now an ideal
time to prune many late-summer-flowering shrubs to keep them
vigorous and flowering well. It’s also not too late to complete the
pruning jobs for August if you haven’t got round to them yet . Here.
I’ve given practical advice for pruning abelia, carpinus,
embothrium, Jasminum officinale, lonicera and passiflora.
Young plants do not require any formative pruning
after planting other than the removal of dead or damaged stems. In
mild areas, where there’s little risk of winter damage, prune after
flowering during late September or early October. Thin out congested
growth by cutting back one-in-three stems that have produced flowers
to a new sideshoot low-down or to near ground level. In cold areas
or after particularly cold winters, much of the top growth may have
been frost-damaged and in this case it is better to cut down all the
shoots to near ground level during May. This is also the best way to
rejuvenate old or neglected plants, but if you find this too drastic
and you have the patience, cut out one-in-three flowered stems each
year (starting with the oldest) over a three-year period instead.
Lonicera (shrubby honeysuckles)
There’s still time to prune shrubby honeysuckles,
such as the popular evergreen L. nitida ‘Baggesen’s Gold’.
Evergreen hedges should be cut back by removing about half the new
growth each year until they reach the desired height. Thereafter,
trim the hedge during May and again in September.
Birch trees need little regular pruning, but when
they are young it is a good idea to cut off lower branches to allow
a clear length of white trunk. Pruned before August they can bleed
profusely, but if pruned now they sap flow will have slowed down.
Deciduous hornbeam trees are best pruned during late
summer because they are prone to bleeding if pruned in spring or
early summer. Most hormbeam trees will form an attractive,
well-balanced canopy without intervention and so require no pruning
other than the removal of crossing or wind-damaged branches. Young
trees should also be encouraged to produce a clear trunk, so remove
lower side branches to gradually raise the canopy as the tree grows.
They can be trained as standards, dense hedges or pleached to look
like a hedge on legs. However, hedges should be trimmed in July to
keep them neat and attractive throughout the summer. Cut back
well-established hedges as required, but new hedges should be cut
back only lightly.
Embothrium (Chilean fire bush)
Grown for its vivid display of brilliant red
flowers, the aptly named Chilean fire bush requires little or no
routine pruning, except the removal of dead or damaged stems.
However, if left to its own devices it will form an attractive
multi-stemmed shrub-like tree, so to create a specimen single
stemmed tree you will have to prune it to shape. Remove all but the
main stem and then keep pruning out any suckering shoots that are
produced in subsequent years. You will need to either excavate a
hole and cut the sucker at its origin with secateurs or cut it off
with a judicious thrust of a sharp spade. Even multi-stemmed
specimens benefit from being thinned out to the strongest four or
five stems. Any routine pruning of wayward or straggly stems is best
carried out after flowering during late summer.
This scented climber should be pruned after
flowering during late summer. Aim to create a framework of
well-spaced branches over the support. Twining stems will soon
provide good coverage. Once well-established, cut back shoots that
have flowered and are not needed to cover the support by pruning to
a sideshoot or bud near the base. Common jasmine tolerates hard
pruning so neglected plants can be reinvigorated by cutting back to
within 50cm (20in) of the base.
Lonicera (common honeysuckle)
Most honeysuckles are deciduous and are best pruned
after flowering during late summer, while evergreen Japanese
honeysuckles (Lonicera japonica) should be pruned during
early spring. Once the honeysuckle has reached the top of its
support, tip-back the shoots to encourage flowering sideshoots to
develop. Well-established plants can become over-congested if left
un-pruned, so thin out the flowered shoots by cutting back by about
one-third to a newer sideshoot lower down. Neglected plants can
become a top-heavy mass of twining stems if not pruned regularly -
with flowers out of sight on the top. Give it a
short-back-and-sides, then reducing the number of main stems
removing any awkwardly placed or crossing stems first. If you want a
complete clear out, deciduous honeysuckles do respond well to hard
pruning in winter to within 30cm (12in) of the ground, but you will
have a big gap and reduced display for a few years.
Passiflora (passion flower)
To make the most of your passion flower
(Passiflora caerulea) you will need to train and prune it
carefully. Aim to create a permanent framework of branches that will
produce a succession of flowering sideshoots. After planting, cut
back plant to about 30cm (12in) to encourage plenty of sideshoots
from low down on the plant. When training against a wall or fence,
space out these stems as they grow about 15cm (6in) apart across the
support. Keep tying in the stems until they reach the top of the
support and then pinch out the growing tip to encourage sideshoots.
On pergolas and arches, trim back all sideshoots except those near
the top which can be trained over the support until the climber’s
framework is complete. Thereafter, simply cut back shoots that have
flowered and fruited to within two or three buds of the permanent
framework of the plant. Replace old specimens with young vigorous
plants rather than attempt renovation with drastic pruning.